Feet of artiodactyls
Sheep are artiodactyls, that is, they walk on only two fingers or toes.
Humans, however, have five fingers on each hand and five toes on each foot.
Is it possible to compare claws of sheep with fingers of humans?
Feet of artiodactyls
There are easy means to consider this question and to keep the conclusion in your mind.
Originally, all vertebrates have a pentamerous limb, that is, they have five "fingers"
on each hand and five "toes" on each foot, respectively, which are collectively
referred to as "phalanges" and numbered consecutively starting at the thumb.
The human hand has already one unique finger, the thumb, which can be opposed to the other
fingers, thus enabling humans to grasp something. The same ability is reduced at the human
big toe, but is still visible at other primates, like apes and monkeys.
The next thought leads us to the dog. His limb, which is homologous to the human thumb,
is special, too, in that it is not used for walking. A dog is walking only on his second
(index finger) to fifth (little finger) phalanges.
This reduction is continued symmetrically in all artiodactyla, that is, both outer
phalanges are further reduced. What is left are our third and fourth phalanx. These
are homologous to the middle and ring finger of humans, respectively (see figure).
| Back to the Homepage | Imprint |
|